Thermodynamics: Stats

Contents

Problems

Problem :

Write down the Gibbs sum. Be sure to get all of the indices correct.

Z G(μ, τ) = e (Nμ-)/τ

Problem :

Give the expression for the absolute probability that a system will be found in the state with N 1 particles and energy .

P(N 1,) =

Problem :

Give an expression for the average value of a property A for a system in diffusive and thermal contact with a "reservoir". A "reservoir" is a huge system next to our smaller system with large energy and number of particles.

< A > =

Problem :

Give an expression for the average number of particles in a system that is in thermal and diffusive contact with a reservoir.

We are looking for < N > , which we can calculate using the formula we just derived.

< N > =

Problem :

Suppose that we have a system that can be unoccupied or can have one particle in a state with energy . Write the Gibbs sum for this system.

One possible state has N = 0 , for which we say that the energy is also zero. So the first term in the sum is 1 . The second possible state has N = 1 , and energy . We can write the total sum as:

Z G = 1 + e μ-/τ

We sometimes simplify this by defining λâÉáe μ/τ , in which case the answer can be written more simply as Z G = 1 + λe -/τ .